There is no resale right in the case of such illustrations. When I was talking about resale right in Canada, I meant creating an illustration and selling it as an original. In the case of a children's book, as you pointed out, there is really a contract, where a user licence is granted and subject to a temporality, geographic space and support conditions. This corresponds to the copyright that is attached to the creation of the illustrations that have been made on the pages.
On January 31st, 2019. See this statement in context.